It has been known that a circular polarization separator sheet which transmits a particular circularly polarized light and reflects other sort of light is provided in display devices such as liquid crystal display devices aiming at enhancement of the luminance of the device. As such a circular polarization separator sheet, there are known a sheet obtained by applying on a substrate a polymer having a cholesteric liquid crystallinity, and orienting and drying the polymer, and a sheet obtained by applying on a substrate a liquid crystal composition comprising a polymerizable monomer having a cholesteric liquid crystallinity, and orienting and polymerizing the monomer. As such a liquid crystal composition, many compositions are known in the prior art (e.g., US Patent Application Publication No. 2005/0045854, Japanese Patent No. 3677632 and JP Hei-8-3111-A).
It is preferable that the liquid crystal composition for preparing the circular polarization separator sheet contains a compound having a Δn value (intrinsic birefringence value) as high as 0.18 or more in order to obtain a high optical property. However, there is a problem that the layer of such a high Δn compound can only be thickened up to at most about 5 μm because otherwise a uniform orientation can not be obtained. In order to obtain a wider reflection bandwidth as the circular polarization separator sheet, those having a thicker thickness are required. Thus, in order to produce a circular polarization separator sheet having a wider reflection bandwidth, it is required to pile up a plurality of layers each having a thickness of about 3 μm with a uniform orientation, which brings about a problem of complicated steps.